The principal fat in chocolate is cocoa butter. Cocoa butter is obtained pressing cocoa beans (normally fermented and roasted) to extract the fat contained within the beans. This fat is polymorphic which means that it can crystallise in a number of solid phases of the same chemical composition that differ among themselves in crystalline structure but yield identical liquid phases on melting. In the textbook Industrial Manufacture and Use (third edition) edited by S. T. Beckett, pages 218 and 219, six polymorphic forms of cocoa butter are mentioned. Their properties are set out in Table 1.
TABLE 1FormMelting point ° C.Chain packingI16-18DoubleII21-22DoubleIII25.5DoubleIV27-29DoubleV34-35TripleVI36Triple
Forms V and VI are the most stable forms of cocoa butter. When chocolate is properly tempered the cocoa butter will crystallize in Form V. Rapid cooling of a molten untempered chocolate mass produces relatively unstable polymorphic forms of cocoa butter. These lower polymorphic forms tend to transform to higher melting, more stable forms. This regrowth of crystals manifests itself in surface defects such as fat bloom. This is a whitish haze or mottling on the surface and makes chocolate appear unpalatable. Fat bloom on untempered chocolate appears rapidly and is particularly severe. The crystal structure of the untempered chocolate gives it a granular mouthfeel. Untempered chocolate does not contract as it crystallizes like tempered chocolate and so is difficult to demould.
The object of tempering, sometimes called pre-crystallization, is to develop a sufficient number of seed crystals to encourage the total fat phase to crystallize as Form V. The most commonly used method of tempering involves the steps of: complete melting; cooling to the point of crystallization; crystallization; and melting out unstable crystals. However other tempering methods are used such as the direct addition of a source of fat crystals in the correct polymorphic form; this operation is called seeding.
Fat bloom can also occur on tempered chocolate. This may be associated with a transition from form V to form VI. Fat bloom on tempered chocolate can occur when filling fats migrate into the chocolate, or when the chocolate is subjected to elevated or fluctuating storage temperatures. If chocolate, which had originally been correctly tempered, is liquefied and then re-cooled it will exhibit the severe bloom of untempered chocolate. This problem of bloom after the chocolate has been liquefied and cooled down can occur in hot countries, or where chocolate products are left in an unsuitable location, such as in a car in the sunshine.
Over the years, many vegetable fats have been identified which can be used as an alternative to cocoa butter. In the textbook Industrial Manufacture and Use (third edition) edited by S. T. Beckett, pages 307 to 322 these are divided into two groups; cocoa butter equivalents (CBEs) which are vegetable fats with similar chemical and physical characteristics to cocoa butter and hence can be used interchangeably with cocoa butter in any recipe, and cocoa butter replacers (CBRs) which are vegetable fats with similar physical, but not chemical, characteristics to cocoa butter that can only be used to replace cocoa butter in more limited applications.
In many countries, the composition of material sold as “chocolate” is controlled by law. Legislation varies from country to country, but material sold as chocolate is often limited to only having fat extracted from cocoa, or to mixtures of fat extracted from cocoa and defined cocoa butter equivalents. Even in countries where it may be legal to sell chocolate containing vegetable fats obtained from sources other than cocoa there may be a strong consumer preference for chocolate made exclusively with milk and/or cocoa derived fat.
Bloom gives an unpleasant aspect to chocolate, and many attempts have been made to try to retard appearance of bloom. One of the most common approaches to solve this problem is to add bloom inhibitors such as milk fat, or proprietary vegetable fat bloom inhibitors such as Prestine™ (Loders Croklaan). Although these have some effect in controlling the fat bloom caused by form V to form VI transitions, they do not control the bloom which occurs after the chocolate is heated to the point where it is liquid and then allowed to cool. In other words, they do not remove the need to re-temper after melting.
JP2003299442 to Fuji Oil describes a non tempering chocolate composition with bloom resistance. However, this composition includes non-cocoa fats such as lauric fat so would not be acceptable as “chocolate”, from a legal point of view, in many countries. Compositions which temper by seeding are also available. Fuji Oil supply seeding material rich in 1,3-behenoyl, 2-oleolglycerol. This triglyceride has a melting point of about 53° C. which means that chocolate containing this material can be heated above its usual melting point but below the melting point of 1,3-behenoyl, 2-oleolglycerol and still cool without bloom as the residual solid 1,3-behenoyl, 2-oleolglycerol is able to re-seed the chocolate. A disadvantage of 1,3-behenoyl, 2-oleolglycerol is that it is not derived from cocoa butter and is not permitted in chocolate in countries such as the members of the European Union.
Industrial Manufacture and Use pages 317 to 320 describes both lauric and non-lauric cocoa butter replacers which do not require tempering. However, these fats are generally not permitted in material sold as chocolate. Significant amounts of cocoa butter cannot be mixed with these without causing soft products and a likelihood of bloom formation. This can make chocolate-like materials based on cocoa butter replacers more prone to bloom than chocolate due to incompatibility with cocoa butter in cocoa powder used to provide the chocolate flavour. Lauric cocoa butter replacers can tolerate up to 5% cocoa butter in the fat phase, white non-lauric cocoa butter replacers can tolerate up to 25% cocoa butter in the fat phase.
One popular way of consuming chocolate is as a chocolate fondue. In a chocolate fondue, food items such as pieces of fruit, biscuits or nuts are dipped into melted chocolate before being eaten. Conventionally, if the chocolate fat phase is predominantly milk fat and/or cocoa butter, the chocolate will bloom when it is cooled down. If the consumer wishes to keep some of the remaining chocolate for another chocolate fondue at a later date, they will simply cool the chocolate at room temperature, or perhaps place it in a fridge. As consumers will not have tempered the chocolate, bloom will rapidly develop. The bloom, although not hazardous, may be mistaken for mould growth and so consumers may discard the chocolate as unappetizing. Similarly, consumers may like to keep some of the chocolate-dipped items to eat at a later date or to use as gifts, but the appearance of fat bloom on the chocolate as it cools will make the chocolate-dipped items unappealing. Pre-packaged chocolate fondues are sold by a number of manufacturers. These often consist of a plastic tub containing a chocolate-like material. The tub can be placed directly in a microwave or in a bain-marie to melt the chocolate-like material at a temperature of around 60° C. The tub is then brought to the table where food items are dipped into it. To avoid the problem of bloom, these pre-packaged “chocolate fondues” generally contain fats other than those derived from milk and or cocoa and so cannot be sold as chocolate in many countries.
There is a need to find a solution to blooming in chocolates where the fat phase consists of cocoa butter and/or milk fat and/or cocoa butter and one or more emulsifier and the chocolate is liquefied and re-solidified without a farther pre-crystallisation step.